The present invention relates to a no-break power supply system for supplying a power to a load in the case of service interuption, more particularly, to an apparatus for protecting a battery provided in the power supply system when components provided therein are broken down.
Such a conventional no-break power supply system is shown in FIG. 1. The system comprises an engine-generator E-G for supplying a power to a load L such as a computer or the like in the case of service interruption for long term, an undervoltage relay RY for detecting service interruption of commercial power supply source, an engine operating means or block PC arranged to receive the output of the relay RY for automatically starting and driving the engine E, a switch S having contacts a and b for selecting the commercial power supply and the engine generator, an overcurrent breaker NFB, a rectifier Rec which also serves as a floating charge device, a battery B connected to the rectifier Rec, and an inverter IV connected to the rectifier Rec and the battery B and having automatic voltage adjusting function.
In the system thus constructed, when components therein are operated correctly, the system operates normally without any trouble. When the system does not operate with the trouble or failure of the rectifier Rec or the trip of the breaker NFB due to any cause, the battery B discharges continuously until the voltage reaches the discharge final voltage, so that the system must be automatically stopped to operate by an automatic stop circuit (not shown) after reached the discharge final voltage. Under this condition, it is necessary for the battery B to take too much time for restoring the charged condition, while the pole substance separation arises often so that life time of the battery is decreased. Under this condition, moreover, sedimentation amount of the pole substance is increased so that sulfation is induced resulting in an exchange of the battery and thus an large expense.
Generally, the floating charge device for battery must be operated in such a manner that it does not affect property of the battery itself thereby increasing the life time thereof and utilizing the battery with stable conditons. To this end, constant voltage charging or constant current charging is usually utilized.
In operation, when service interruption occurred, the supply from commercial power source is immediately changed to the supply from the battery. In this case, when the battery itself has poorcapacity, overcharging current flows in the battery which serves as a load for the generator, so that the generator becomes overload condition.
If the capacity of the generator is increased it becomes expense and more overcurrent flows in the battery so that the above described pole substance separation arises therein, resulting in a decrease of the battery life-time.